Recent theories suggest that reward-based choice reflects competition between value signals in the ventromedial prefrontal cortex (vmPFC). We tested this idea by recording vmPFC neurons while macaques performed a gambling task with asynchronous offer presentation. We found that neuronal activity shows four patterns consistent with selection via mutual inhibition: (1) correlated tuning for probability and reward size, suggesting that vmPFC carries an integrated value signal; (2) anti-correlated tuning curves for the two options, suggesting mutual inhibition; (3) neurons rapidly come to signal the value of the chosen offer, suggesting the circuit serves to produce a choice; and (4) after regressing out the effects of option values, firing rates still could predict choice—a choice probability signal. In addition, neurons signaled gamble outcomes, suggesting that vmPFC contributes to both monitoring and choice processes. These data suggest a possible mechanism for reward-based choice and endorse the centrality of vmPFC in that process. •vmPFC neurons signal gamble probability and reward size in a common currency format•vmPFC neurons antagonistically signal values of competing offers•vmPFC neurons signal chosen values and not unchosen values•Residual variability in vmPFC firing immediately before selection predicts choices Strait et al. show that during reward-based choice, vmPFC neurons signal gamble probability and reward size in a common currency format and antagonistically signal values of competing offers, consistent with value comparison through mutual inhibition between reward representations.